Re: [PATCH] Clean up old names in tty code to current names

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Mon, Jul 10, 2006 at 11:10:32AM -0400, Valdis.Kletnieks@vt.edu wrote:
> On Mon, 10 Jul 2006 16:19:06 BST, Alan Cox said:
> > Ar Llu, 2006-07-10 am 10:57 -0400, ysgrifennodd Jon Smirl:
> > > > A few apps do rely on /proc/tty/drivers for the major-minor
> > > > to device name mapping. /dev/vc/0 does not exist (unless
> > > > created manually) without devfs.
> > > 
> > > This is why I questioned if /proc/tty was really in use, it contains
> > > an entry that is obviously wrong for my system.
> > 
> > Which tools already know about. What is so hard to understand about the
> > idea that pointless random changes break stuff and don't fix things.
> 
> On the other hand, a case can be made that if userspace already knows about
> the fact the thing is totally broken

Maybe - what if userspace is looking up /dev/tty0 in /proc/tty/drivers
and happens to know that it's called /dev/vc/0, because it's working
around this known idiosyncrasy of the kernel ?  If you change tty/drivers
to be the more correct /dev/tty0, such a program would needlessly break.

> fixing it won't break anything.

How can you be certain - I think that's Alan's point (if it isn't,
that's my point.)  The answer is you can't, so in order to maintain
ABI compatibility (and yes, this *IS* part of the kernel ABI) it
must be left exactly as-is.

> The only case is that some *already* terminally broken stuff may break
> further.

That "terminally broken stuff" might just happen to work with today's
kernels.  Even so, that's no reason to pile in additional user-visible
changes which could potentially have adverse effects.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core